1. Field of Invention
The present invention relates to a switch box. In particular, the invention relates to a switch box suitable to be installed on a vehicle such as an automobile and to a vehicle having the switch box installed in it.
2. Description of Related Art
In a vehicle such as an automobile, a switch box accommodating various kinds of functional component parts such as fuses, relays, and the like has been used. In the switch box, circuits are turned on and off by plug-in type relays, and the power supply is cut off by fuses under abnormal conditions. Because such a switch box accommodates many component parts and is large, a switch box miniaturized by using an intelligent power switch instead of the fuses and the relays has been developed. By using the intelligent power switch, the switch box is allowed to have a monitor function of generating an alarm when abnormal electric current is detected during driving of the vehicle. When the abnormality has been eliminated, the intelligent power switch returns to the original state automatically.
However, because the intelligent power switch is composed of electronic elements, it has a feature that it has a large heat output and is destroyed at high temperatures. Thus, the switch box using such an intelligent power switch is provided with heat dispersion means (see Japanese Laid-Open Patent Publications No. 5-78126 and 7-122867).
In the switch box disclosed in Japanese Laid-Open Patent Publication No. 5-78126, as shown in FIG. 3, a bus bar 31 is laid on the upper surface of a substrate 30 accommodated inside the box. Intelligent power switches 32 are installed on the bus bar 31. Heat generated by the intelligent power switches 32 can be dispersed through the bus bar 31. Because the lower surface of the bus bar 31 is laid on and in contact with the upper surface of the substrate 30, the bus bar 31 requires a large space on the substrate 30. Thus, the substrate 30 is necessarily large and hence expensive.
In the switch box disclosed in Japanese Laid-Open Patent Publication No. 7-122867, as shown in FIG. 4, a frame-shaped heat sink 34 is erected on the upper surface of a substrate 33 accommodated inside the box. Intelligent power switch 35 is installed on a side surface of the heat sink 34. Accordingly, heat generated by the intelligent power switch 35 can be dispersed through the heat sink 34. In this switch box, the heat sink 34 has merely a function of removing the heat generated by the intelligent power switch 35 and of holding the intelligent power switch 35 fixed thereto.